EP0350947B1

EP0350947B1 - Radio channel control method

Info

Publication number: EP0350947B1
Application number: EP89112954A
Authority: EP
Inventors: Noboru Saegusa; Yukihiro Shimura; Hideki Toyama; Yuji Ohta; Shoji Fuse; Koji Ono
Original assignee: Toshiba Corp; NEC Corp; Nippon Telegraph and Telephone Corp; Tokyo Shibaura Electric Co Ltd; Nippon Electric Co Ltd; NTT Mobile Communications Networks Inc
Current assignee: Nec Corp En Nippon Telegraph And Telephone
Priority date: 1988-07-15
Filing date: 1989-07-14
Publication date: 1996-05-15
Anticipated expiration: 2009-07-14
Also published as: KR900002584A; KR920010106B1; JPH0226141A; EP0350947A3; DE68926476T2; DE68926476D1; US5086451A; EP0350947A2

Description

The present invention relates to a radio channel control method for connecting a plurality of stationary apparatuses and a plurality of portable mobile telephones through radio channels and, more particularly, to a radio channel control method in a mobile communication apparatus such as a cordless telephone used in a relatively small area.
Fig. 1 is a block diagram showing an arrangement of a cordless telephone set. In Fig. 1, reference numeral 1 denotes a main apparatus connected to a telephone line and having a line control function; 10_l to 10_n, a plurality of stationary apparatuses each having a radio receiver/transmitter; and 20_l to 20_n, portable telephones. The main apparatus 1 and the stationary apparatuses 10₁ to 10_n are coupled through wire lines L_l to L_n. The portable telephones 20_l to 20_n and the stationary apparatuses 10_l to 10_n are present in a single area A and use a single frequency as a radio control channel. For this reason, the main apparatus 1 is set in a main state (first state) in which only a stationary apparatus designated by a control signal is controlled through a radio channel. Therefore, the remaining stationary apparatuses are set in a sub state (second state) in which they wait for designation by the control signal.
In the conventional radio channel control method, however, when a control signal cannot be received even once due to an error in a wire line between the main apparatus 1 and the stationary apparatus, all the stationary apparatuses are set in the sub state, and the radio channel cannot be connected. This drawback will be exemplified below.
Fig. 2 is a chart showing a conventional radio channel control method (see US-A-4656653). For the sake of simplicity, an arrangement comprises the main apparatus, first and second stationary apparatuses, and first and second portable telephones. Assume that the first stationary apparatus is designated in the main state by the main apparatus.
In Fig. 2, the first portable telephone transmits a call signal S₂₁ to the first stationary apparatus in response to a call operation by a user. Upon reception of the call signal S₂₁, the first stationary apparatus designated in the main state transmits a call signal S₂₂ to the main apparatus, and transmits a call response signal S₂₃ including communication channel information to the first portable telephone. Thereafter, the first stationary apparatus is switched to the sub state by itself. Subsequently, upon reception of the call response signal S₂₃, the first portable telephone is switched to a communication channel, and transmits a channel switching signal S₂₄ to the first stationary apparatus. When the first stationary apparatus receives the channel switching signal s₂₄, it transmits an AF (Audio Frequency)-ON signal S₂₅ to the first portable telephone, and transmits a connection end signal S₂₆ to the main apparatus, thus enabling communication with the first portable telephone. Meanwhile, when the main apparatus receives the call signal S₂₂, it transmits a state designation signal S₂₇ to the second stationary apparatus to switch the second stationary apparatus to the main state. Upon reception of the connection end signal S₂₆ from the first stationary apparatus, the main apparatus connects the first portable telephone and the telephone line.
However, when a given error occurs in the wire line and the second stationary apparatus cannot receive the state designation signal from the main apparatus, the second stationary apparatus is kept in the sub state. Therefore, in this state, even if a user of the second portable telephone transmits a call signal S₂₈, the radio channel cannot be connected since the second stationary apparatus is kept in the sub state.
As described above, in the conventional method, since the main apparatus does not confirm the states of the stationary apparatuses, if a given error occurs in the wire line and the state designation signal cannot be received even once, the radio channel cannot be connected.
It is therefore a principal object of the present invention to provide a radio channel control method in which a main apparatus confirms states of stationary apparatuses, so that even if an error occurs in a wire line, a radio channel can be connected. This object is solved with the features of the claims.
There is disclosed a radio channel control method for a system comprising a main apparatus connected to a telephone line and having a line control function, a plurality of stationary apparatuses connected to the main apparatus and each having a radio transmitter/receiver, and a portable telephone capable of communicating with the stationary apparatuses through a radio channel, wherein the main apparatus designates each of the stationary apparatuses in a first or second state to control communication with the portable telephone, monitors a state signal including information of the first or second state transmitted from each of the stationary apparatuses, and when the state signal from a given stationary apparatus does not coincide with a state of the given stationary apparatus designated by the main apparatus, transmits a state designation signal to the given stationary apparatus to coincide with the state designated by the main apparatus.

Fig. 1 is a block diagram showing an arrangement of a cordless telephone set;
Fig. 2 is a chart showing a conventional radio channel control method; and
Fig. 3 is a chart showing a radio channel control method according to the present invention.

Fig. 3 is a chart showing a radio channel control method according to the present invention. Assume that this embodiment comprises a main apparatus, first and second stationary apparatuses, and first and second portable telephones for the sake of simplicity as in Fig. 2. The first stationary apparatus is set in a main state, and the second stationary apparatus is set in a sub state. The two stationary apparatuses periodically send a state signal including main/sub information to the main apparatus.
The first portable telephone sends a call signal S₁ to the first stationary apparatus in response to a call operation by a user. Upon reception of the call signal S₁, the first stationary apparatus which is designated in the main state by the main apparatus transmits a call signal S₂ to the main apparatus, and transmits a call response signal S₃ including communication channel information to the first portable telephone. Thereafter, the first stationary apparatus is switched to the sub state by itself. Upon reception of the call response signal S₃, the first portable telephone is switched to a communication channel, and transmits a channel switching signal S₄ to the first stationary apparatus. Upon reception of the channel switching signal S₄, the first stationary apparatus transmits an AF-ON signal S₅ to the first portable telephone, and transmits a connection end signal S₆ to the main apparatus.
Meanwhile, when the main apparatus receives the call signal S₂, it changes stored main/sub information of the first stationary apparatus from the main state to the sub state, and changes the stored information of the second stationary apparatus from the sub state to the main state on the basis of a state signal S₀ supplied from the first stationary apparatus. In this state, the main apparatus compares the stored main/sub information with a state signal S₇ transmitted from the second stationary apparatus. As a result, when two pieces of information do not coincide with each other, the main apparatus transmits a state designation signal S₈ to the second stationary apparatus to switch it to the main state.
When an error occurs in the wire line connecting the main apparatus and the second stationary apparatus, the second stationary apparatus cannot receive the state designation signal S₈ from the main apparatus. However, since the second stationary apparatus periodically transmits the state signal including main/sub information, it can transmit the next state signal S₉ to cause the main apparatus to detect again that the two pieces of information do not coincide with each other. Thus, the second stationary apparatus can receive the next state designation signal S₁₀ from the main apparatus and can be switched to the main state.
Thereafter, when the second stationary apparatus receives a call signal S₁₁ from the second portable telephone, it transmits a call signal S₁₂ to the second portable telephone, and also transmits a call signal S₁₃ to the main apparatus. Upon reception of a channel switching signal S₁₄ from the second portable telephone, the second stationary apparatus transmits an AF-ON signal S₁₅ to the second portable telephone, and transmits a connection end signal S₁₆ to the main apparatus, thus enabling communication with the second portable telephone.
In the description of the embodiment, the number of stationary apparatuses is two. When three or more stationary apparatuses are arranged, one of the stationary apparatuses other than the stationary apparatus which has been changed to the sub state can be selected and can be switched to the main state by the state designation signal.
According tc the present invention, the stationary apparatus periodically transmits a state signal including main/sub information. Thus, even if the main apparatus cannot transmit a state designation signal to the stationary apparatus due to an error in a wire line, the main apparatus can transmit the state designation signal again in response to the next state signal from the stationary apparatus. In this manner, the main apparatus can reliably designate the main/sub state of the stationary apparatus, and a communication disable state caused by an error in a wire line can be prevented.
When a state signal cannot be received from a stationary apparatus within a predetermined period of time or when main/sub information of a state signal varies in every reception, the main apparatus can determine that the corresponding stationary apparatus is abnormal, thus providing great practical advantages.

Claims

A radio channel control method for a system comprising
a) a main apparatus (1) connected to a telephone line and having a line control function,

b) a plurality of stationary apparatuses (10) connected to said main apparatus (1) and each having a radio transmitter/receiver, and

c) a portable telephone (20) capable of communicating with said stationary apparatuses (10) through a radio channel,
wherein

d) a portable telephone (20) sends a call signal to a stationary apparatus (10),

e) upon reception of this signal, the stationary apparatus (10) which has been designated into the first state by the main apparatus (1), transmits a call signal to the main apparatus (1) and transmits a call response signal, including communication channel information, to the portable telephone (20),

f) thereafter, the stationary apparatus (10) switches itself to the second state,

g) upon reception of the call response signal, the portable telephone (20) switches to a communication channel and transmits a channel switching signal to the stationary apparatus (10), and

h) upon reception of the channel switching signal the stationary apparatus (10) transmits an AF-ON signal to the portable telephone (20) and transmits a connection end signal to the main apparatus (1),
characterized in that

i) the first state of a stationary apparatus (10) is a state where a radio channel can be connected,

j) the second state of a stationary apparatus (10) is a state in which the stationary apparatus (10) is either inactive or involved in communication with a portable telephone (10),

k) the stationary apparatuses (10) periodically transmit state signals to the main apparatus (1), thereby indicating whether they are in the first or the second state,

l) after transmission of a call response to a portable telephone (20), the stationary apparatus (10) switches itself to the second state, and

m) any of the stationary apparatuses (10) other than the stationary apparatus which has been changed to a second state can be selected and can be switched to the first state by a state designation signal coming from the main apparatus (1).
A method according to claim 1, wherein the first state is a state in which one of said plurality of stationary stations (10) is connected to said portable telephone (20) through the radio channel, and the second state is a state wherein all the stationary apparatuses (10) excluding said one stationary apparatus are not connected to said portable telephone (20) through the radio channel.
A method according to claim 1 or 2, wherein each of said stationary apparatuses periodically sends the state signal to said main apparatus during a communication standby state, in which none of the stationary apparatuses (10) is ) connected to the portable telephone (20).